Isolating and evaluating lactic acid bacteria strains with or without sucrose for effectiveness of silage fermentation

Abstract

AbstractThe aim of this study was to screen and evaluate lactic acid bacteria strains for their ability to ferment alfalfa, Leymus chinensis and native grass into silage. We isolated 186 lactic acid bacteria strains from alfalfa, native grass and selected eight strains by acid production test and growth rate test. The eight stains were identified using morphological observations, Gram staining, physiological and biochemical tests, an acid tolerance test and 16S rDNA sequencing. All eight strains (LP1, LP2, LC1, LC2, PP1, PP2, EF1 and EF2) grew at pH 4.0 and 6.5%NaCl. Strains LP1 and LP2 were identified as Lactobacillus plantarum, LC1 and LC2 as Lactobacillus casei, PP1 and PP2 as Pediococcus pentosaceus, EF1 as Enterococcus faecalis, and EF2 as Enterococcus faecium based on their 16S rDNA sequences. The eight strains and two commercial inoculants (PS and CL) were added with or without sucrose to native grass, L. chinensis, and alfalfa to produce silage. All eight screened strains decreased the pH and ammonia nitrogen (N) content and increased the lactic acid content of alfalfa silages. No butyric acid was detected in the L. chinensis and alfalfa silages. Addition of sucrose with the screened strains resulted in lower pH and ammonia N content, and higher lactic acid content and total fermentation acids content in all three silages. The eight strains improved the fermentation quality of alfalfa silage. All strains were more effective when supplemented with sucrose. No efficient lactic acid bacteria strain was found for ensiling the native grass, but the high fermentation quality native grass silage could be obtained using the combination of lactic acid bacteria strains and 2% sucrose.